U.S. patent application number 12/812844 was filed with the patent office on 2011-02-24 for dynamoelectric machine.
This patent application is currently assigned to Mitsubishi Electric Corporation. Invention is credited to Hiroyuki Akita, Moriyuki Hazeyama, Masaya Inoue, Takeshi Mori, Masao Morita, Shinji Nishimura, Ryuichi Shimomura, Kanji Shinkawa, Kazunori Tanaka, Toshiyuki Yoshizawa.
Application Number | 20110043068 12/812844 |
Document ID | / |
Family ID | 40956754 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110043068 |
Kind Code |
A1 |
Yoshizawa; Toshiyuki ; et
al. |
February 24, 2011 |
DYNAMOELECTRIC MACHINE
Abstract
A dynamoelectric machine that can suppress increases in rotor
inertia to extend belt service life and increase field
magnetomotive force to increase output. In the dynamoelectric
machine, first and second magnetic guidance members are fitted into
first and second holding grooves that are disposed so as to extend
axially on facing portions of first and second trough portions
radially outside inner wall surfaces, and are disposed so as to
span over first and second trough portions. First and second
permanent magnets that are magnetically oriented in a reverse
direction to a magnetic field that originates from a field coil are
fitted into and held by interfitting grooves of the first and
second magnetic guidance members so as to face inner
circumferential surfaces near tip ends of second and first
claw-shaped magnetic pole portions so as to have a predetermined
clearance.
Inventors: |
Yoshizawa; Toshiyuki;
(Tokyo, JP) ; Inoue; Masaya; (Tokyo, JP) ;
Shinkawa; Kanji; (Tokyo, JP) ; Morita; Masao;
(Tokyo, JP) ; Hazeyama; Moriyuki; (Tokyo, JP)
; Mori; Takeshi; (Tokyo, JP) ; Akita;
Hiroyuki; (Tokyo, JP) ; Shimomura; Ryuichi;
(Tokyo, JP) ; Tanaka; Kazunori; (Tokyo, JP)
; Nishimura; Shinji; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
40956754 |
Appl. No.: |
12/812844 |
Filed: |
April 28, 2008 |
PCT Filed: |
April 28, 2008 |
PCT NO: |
PCT/JP2008/058191 |
371 Date: |
July 14, 2010 |
Current U.S.
Class: |
310/181 |
Current CPC
Class: |
H02K 21/044
20130101 |
Class at
Publication: |
310/181 |
International
Class: |
H02K 21/04 20060101
H02K021/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2008 |
JP |
2008 031647 |
Feb 13, 2008 |
JP |
2008 031658 |
Claims
1. A dynamoelectric machine comprising: a rotor comprising: a pole
core comprising: a boss portion; a pair of yoke portions that are
disposed so as to extend radially outward from two axial end edge
portions of said boss portion; and a plurality of claw-shaped
magnetic pole portions that are disposed so as to extend in an
axial direction alternately from each of said pair of yoke
portions, and that are arranged circumferentially so as to
intermesh with each other, a trough portion that curves radially
inward being formed on a portion of each of said yoke portions
between circumferentially adjacent claw-shaped magnetic pole
portions, and said pole core being prepared such that tip end
portions of said claw-shaped magnetic pole portions overlap with
said yoke portions axially, and being fixed to a rotating shaft
that is inserted through a central axial position of said boss
portion; and a field coil that is housed inside a space that is
surrounded by said boss portion, said pair of yoke portions, and
said plurality of claw-shaped magnetic pole portions; and a stator
that is disposed so as to surround an outer circumference of said
rotor so as to have a predetermined air gap interposed, said
dynamoelectric machine comprising: a magnetic guidance member that
is made of a magnetic material and is disposed so as to span said
trough portion; and a permanent magnet that is disposed on said
magnetic guidance member so as to face an inner circumferential
surface near a tip end of said claw-shaped magnetic pole portions
so as to have a predetermined clearance, and that is magnetically
oriented in a reverse direction to an orientation of a magnetic
field produced by said field coil.
2. The dynamoelectric machine according to claim 1, wherein a
direction of magnetization of said permanent magnet is
approximately perpendicular to said inner circumferential surface
near said tip end of said facing claw-shaped magnetic pole
portion.
3. The dynamoelectric machine according to claim 1, wherein an
outer circumferential surface of said permanent magnet is
approximately parallel to said inner circumferential surface near
said tip end of said facing claw-shaped magnetic pole portion.
4. The dynamoelectric machine according to claim 3, wherein an
inner circumferential surface and an outer circumferential surface
of said permanent magnet are parallel.
5. The dynamoelectric machine according to claim 1, wherein:
holding grooves are recessed near roots of said claw-shaped
magnetic pole portions of said pole core from radially outside said
yoke portions toward said field coil so as to have openings at
respective facing portions radially outside an inner wall surface
of said trough portion, and so as to have a groove direction
oriented axially; an interfitting groove is recessed into said
magnetic guidance member so as to have an opening in a direction
that is positioned radially outside said magnetic guidance member
that is fitted into and held by said holding grooves, and so as to
have a groove direction oriented axially; said magnetic guidance
member is disposed so as to span said trough portion by being
fitted into and held by said facing holding grooves; said permanent
magnet is held by said magnetic guidance member by being fitted
into said interfitting groove; and said permanent magnet is
positioned entirely in an inside diameter portion of said
claw-shaped magnetic pole portions when viewed from radially
outside.
6. The dynamoelectric machine according to claim 1, wherein:
holding grooves are recessed near roots of said claw-shaped
magnetic pole portions of said pole core from radially outside said
yoke portions toward said field coil so as to have openings at
respective facing portions radially outside an inner wall surface
of said trough portion, and so as to have a groove direction
oriented axially; an interfitting groove is recessed into said
magnetic guidance member so as to have an opening in a direction
that is positioned radially outside said magnetic guidance member
that is fitted into and held by said holding grooves, and so as to
have a groove direction oriented axially; said magnetic guidance
member is disposed so as to span said trough portion by being
fitted into and held by said facing holding grooves; said permanent
magnet is prepared so as to have an axial length that is shorter
than said magnetic guidance member, and is held by said magnetic
guidance member by being fitted into said interfitting groove such
that a center of said permanent magnet is offset closer to said
field coil than a center of said magnetic guidance member in the
axial direction; and a portion of said permanent magnet is exposed
from said claw-shaped magnetic pole portions when viewed from
radially outside, and a remaining portion is positioned in an
inside diameter portion of said claw-shaped magnetic pole portions,
and said permanent magnet is magnetically oriented such that an
extension of a direction of magnetization that passes through said
center of said permanent magnet is directed at said inner
circumferential surface near said tip end of said claw-shaped
magnetic pole portion.
7. The dynamoelectric machine according to claim 6, wherein at
least a region near said field coil in an axial position of said
interfitting groove is formed so as to have a groove shape that has
a gradient that is inclined relative to said rotating shaft in a
direction that is radially inward from a radially outer position
toward said field coil, and said permanent magnet is held by said
magnetic guidance member by being fitted into said region of said
interfitting groove that is inclined at said gradient.
8. The dynamoelectric machine according to claim 6, wherein:
bending lines are formed on said pole core at boundaries between
said claw-shaped magnetic pole portions and said yoke portions; and
said magnetic guidance member is fitted into and held by said
holding grooves so as to be positioned between a point of
intersection between said holding grooves and said bending lines,
and an axially outer end surface of said yoke portions.
9. The dynamoelectric machine according to claim 1, wherein said
permanent magnet is covered by a protective cover.
10. The dynamoelectric machine according to claim 1, wherein said
permanent magnet is molded in a resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dynamoelectric machine
such as an automotive alternator, etc., and particularly relates to
a Lundell rotor.
BACKGROUND ART
[0002] Automotive alternators that use Lundell rotors have been
used in automobiles for decades. Loads from electrical equipment
that is mounted due to environmental issues have been increasing
rapidly in recent years, and further increases in generated power
are being sought from Lundell rotors.
[0003] Increasing field magnetomotive force of the rotor is most
effective for increasing output of Lundell dynamoelectric machines.
However, if the amount of magnetic flux that passes through the
rotor is increased by increasing the field magnetomotive force,
sizes of respective portions of the rotor are consequently required
to be designed such that appropriate magnetic flux density is
achieved so as to avoid magnetic saturation of rotor magnetic path
portions. From a design perspective, it is necessary to ensure that
yoke portions are not magnetically saturated from root portions of
claw-shaped magnetic pole portions.
[0004] In magnetic path design of a Lundell rotor, methods have
been proposed in which design is performed such that magnetic path
cross-sectional area of a yoke portion is sufficiently large
relative to root magnetic path cross-sectional area of claw-shaped
magnetic pole portions as a design that alleviates magnetic
saturation of the rotor (see Patent Literature 1, for example).
[Patent Literature 1]
[0005] Japanese Patent Laid-Open No. HEI 11-243673 (Gazette)
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0006] However, in the above conventional Lundell rotor, axial
thickness of the yoke portion is increased significantly as a
result of having designed the magnetic flux density of the
respective portions appropriately, increasing rotor inertia
significantly.
[0007] In automotive alternators, engine power is transmitted
through a belt and pulley. For this reason, if rotor inertia is
increased, when there is engine rotational pulsation, etc., inertia
torque of the rotor is increased, and one problem is that driving
torque transmitting capacity of the belt may be exceeded, giving
rise to belt slippage, and shortening belt service life.
[0008] The present invention aims to solve the above problems and
an object of the present invention is to provide a dynamoelectric
machine that can suppress increases in rotor inertia to extend belt
service life and increase field magnetomotive force to increase
output by disposing a permanent magnet that generates magnetic flux
to cancel out magnetic flux that originates from a field coil to
alleviate magnetic saturation of rotor magnetic path portions, and
reducing thickness beyond conventional design limits of a yoke
portion that contributes to rotor inertia.
Means for Solving the Problem
[0009] In order to achieve the above object, according to one
aspect of the present invention, there is provided a dynamoelectric
machine including: a rotor including: a pole core including: a boss
portion; a pair of yoke portions that are disposed so as to extend
radially outward from two axial end edge portions of the boss
portion; and a plurality of claw-shaped magnetic pole portions that
are disposed so as to extend in an axial direction alternately from
each of the pair of yoke portions, and that are arranged
circumferentially so as to intermesh with each other, a trough
portion that curves radially inward being formed on a portion of
each of the yoke portions between circumferentially adjacent
claw-shaped magnetic pole portions, and the pole core being
prepared such that tip end portions of the claw-shaped magnetic
pole portions overlap with the yoke portions axially, and being
fixed to a rotating shaft that is inserted through a central axial
position of the boss portion; and a field coil that is housed
inside a space that is surrounded by the boss portion, the pair of
yoke portions, and the plurality of claw-shaped magnetic pole
portions; and a stator that is disposed so as to surround an outer
circumference of the rotor so as to have a predetermined air gap
interposed. The dynamoelectric machine includes: a magnetic
guidance member that is made of a magnetic material and is disposed
so as to span the trough portion; and a permanent magnet that is
disposed on the magnetic guidance member so as to face an inner
circumferential surface near a tip end of the claw-shaped magnetic
pole portions so as to have a predetermined clearance, and that is
magnetically oriented in a reverse direction to an orientation of a
magnetic field produced by the field coil.
EFFECTS OF THE INVENTION
[0010] According to the present invention, magnetic guidance
members are disposed so as to span trough portions, and permanent
magnets are disposed on the magnetic guidance members so as to face
inner circumferential surfaces near tip ends of claw-shaped
magnetic pole portions so as to have a predetermined clearance, and
are magnetically oriented in a reverse direction to a direction of
a magnetic field that is produced by a field coil. In permanent
magnets that are disposed at a first axial end, magnetic flux that
originates from the permanent magnets flows through the inner
circumferential surfaces near the tip ends of the facing
claw-shaped magnetic pole portions from outer circumferential
surfaces of the permanent magnets. On the other hand, in permanent
magnets that are disposed at a second axial end, magnetic flux that
originates from the permanent magnets is diverted circumferentially
from inner circumferential surfaces of the permanent magnets and
guided toward a yoke portion by the magnetic guidance members, and
subsequently guided to a central portion of a pole core by the yoke
portion.
[0011] Thus, because magnetic flux that originates from the
permanent magnets flows through a closed magnetic circuit inside
the rotor in a reverse direction to the magnetic flux that is
generated by the passage of electric current to the field coil,
magnetic saturation of the rotor is alleviated. In addition, the
magnetic flux that is guided from the permanent magnets to the yoke
portion by the magnetic guidance members flows in a reverse
direction to the magnetic flux that originates from the field coil
that flows through the yoke portion from the central portion of the
pole core to the portions near the root ends of the claw-shaped
magnetic pole portions, and acts to alleviate magnetic saturation
of the yoke portion. As a result, even if field magnetomotive force
increases and the amount of magnetic flux increases, the yoke
portion is less likely to become magnetically saturated, enabling
thickness of the yoke portion to be reduced beyond conventional
design concepts, and rotor inertia is reduced, eliminating the need
to adopt countermeasures against belt slippage on a clutch pulley,
etc., due to rotational inertia torque. In addition, field
magnetomotive force can be increased, enabling increased
output.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross section that schematically shows an
automotive alternator according to Embodiment 1 of the present
invention;
[0013] FIG. 2 is a perspective that shows a rotor that can be used
in the automotive alternator according to Embodiment 1 of the
present invention;
[0014] FIG. 3 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in the automotive
alternator according to Embodiment 1 of the present invention;
[0015] FIG. 4 is a schematic diagram for explaining flow of
magnetic flux in the automotive alternator according to Embodiment
1 of the present invention;
[0016] FIG. 5 is a schematic diagram for explaining flow of
magnetic flux in the automotive alternator according to Embodiment
1 of the present invention;
[0017] FIG. 6 is an end elevation that shows a vicinity of a first
magnetic flux guidance member in the rotor that can be used in the
automotive alternator according to Embodiment 1 of the present
invention;
[0018] FIG. 7 is an end elevation that shows a vicinity of a first
magnetic flux guidance member in a rotor that functions as a
comparative example;
[0019] FIG. 8 is a graph that shows a relationship between field
magnetomotive force and stator interlinked magnetic flux in the
automotive alternator according to Embodiment 1 of the present
invention;
[0020] FIG. 9 is a graph that shows generated power relative to
rotational frequency in the automotive alternator according to
Embodiment 1 of the present invention;
[0021] FIG. 10 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 2
of the present invention;
[0022] FIG. 11 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in the automotive
alternator according to Embodiment 2 of the present invention;
[0023] FIG. 12 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 3
of the present invention;
[0024] FIG. 13 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in the automotive
alternator according to Embodiment 3 of the present invention;
[0025] FIG. 14 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 4
of the present invention;
[0026] FIG. 15 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in an automotive
alternator according to Embodiment 5 of the present invention;
[0027] FIG. 16 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in an automotive
alternator according to Embodiment 6 of the present invention;
[0028] FIG. 17 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in an automotive
alternator according to Embodiment 7 of the present invention;
[0029] FIG. 18 is an end elevation that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 8
of the present invention;
[0030] FIG. 19 is an end elevation that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 9
of the present invention;
[0031] FIG. 20 is a cross section that schematically shows an
automotive alternator according to Embodiment 10 of the present
invention;
[0032] FIG. 21 is a perspective that shows a rotor that can be used
in the automotive alternator according to Embodiment 10 of the
present invention;
[0033] FIG. 22 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in the automotive
alternator according to Embodiment 10 of the present invention;
[0034] FIG. 23 is a cross section that shows part of the rotor that
can be used in the automotive alternator according to Embodiment 10
of the present invention;
[0035] FIG. 24 is a cross section that shows part of the rotor that
can be used in the automotive alternator according to Embodiment 10
of the present invention;
[0036] FIG. 25 is a schematic diagram for explaining flow of
magnetic flux in the automotive alternator according to Embodiment
10 of the present invention;
[0037] FIG. 26 is a schematic diagram for explaining flow of
magnetic flux in the automotive alternator according to Embodiment
10 of the present invention;
[0038] FIG. 27 is a graph that shows a relationship between field
magnetomotive force and stator interlinked magnetic flux in the
automotive alternator according to Embodiment 10 of the present
invention;
[0039] FIG. 28 is a graph that shows generated power relative to
rotational frequency in the automotive alternator according to
Embodiment 10 of the present invention;
[0040] FIG. 29 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 11
of the present invention;
[0041] FIG. 30 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 12
of the present invention;
[0042] FIG. 31 is an end elevation that shows a rotor that can be
used in an automotive alternator according to Embodiment 13 of the
present invention; and
[0043] FIG. 32 is an end elevation that shows a rotor that can be
used in an automotive alternator according to Embodiment 14 of the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
[0044] FIG. 1 is a cross section that schematically shows an
automotive alternator according to Embodiment 1 of the present
invention, FIG. 2 is a perspective that shows a rotor that can be
used in the automotive alternator according to Embodiment 1 of the
present invention, and FIG. 3 is a perspective that explains a
method for mounting a permanent magnet to a magnetic guidance
member in the automotive alternator according to Embodiment 1 of
the present invention.
[0045] In FIGS. 1 through 3, an automotive alternator 1 includes: a
case 4 that is constituted by a front bracket 2 and a rear bracket
3 that are each made of aluminum in an approximate cup shape; a
rotor 13 that is rotatably disposed inside the case 4 such that a
rotating shaft 16 is supported by means of bearings 5 in the case
4; a pulley 6 that is fixed to an end portion of the rotating shaft
16 that projects outward at a front end of the case 4; fans 7 that
are fixed to two end surfaces in an axial direction of the rotor 13
(hereinafter "axial direction"); a stator 10 that is fixed to the
case 4 so as to surround an outer circumference of the rotor 13 so
as to have a constant air gap 29 relative to the rotor 13; a pair
of slip rings 8 that are fixed to a rear end of the rotating shaft
16, and that supply current to the rotor 13; and a pair of brushes
9 that are disposed inside the case 4 so as to slide on the
respective slip rings 8. Moreover, although not shown, a rectifier
that rectifies an alternating current that is generated in the
stator 10 into direct current, and a voltage regulator that adjusts
magnitude of an alternating voltage generated in the stator 10,
etc., are disposed inside the case 4.
[0046] The stator 10 includes: a cylindrical stator core 11; and a
stator coil 12 that is mounted to the stator core 11, and in which
an alternating current arises due to changes in magnetic flux from
a field coil 14 (described below) that accompany rotation of the
rotor 13.
[0047] The rotor 13 includes: a field coil 14 that generates
magnetic flux on passage of an excitation current; a pole core 15
that is disposed so as to cover the field coil 14 and in which
magnetic poles are formed by that magnetic flux; and the rotating
shaft 16, which is fitted through a central axial position of the
pole core 15.
[0048] The pole core 15 is configured so as to be divided into
first and second pole core bodies 17 and 21 that are each prepared
by a cold forging manufacturing method using a low carbon steel
such as S10C, for example.
[0049] The first pole core body 17 has: a first boss portion 18
that has an outer circumferential surface that has a cylindrical
shape, and in which a rotating shaft insertion aperture 18a is
formed so as to pass through a central axial position; a thick
ring-shaped first yoke portion 19 that is disposed so as to extend
radially outward from a first end edge portion of the first boss
portion 18; and first claw-shaped magnetic pole portions 20 that
are disposed so as to extend toward a second axial end from outer
circumferential portions of the first yoke portion 19. Eight, for
example, first claw-shaped magnetic pole portions 20 are formed so
as to have a tapered shape in which a radially-outermost surface
shape is an approximately trapezoidal shape, a circumferential
width gradually becomes narrower toward a tip end, and a radial
thickness gradually becomes thinner toward the tip end, and are
arranged on the outer circumferential portions of the first yoke
portion 19 at a uniform angular pitch circumferentially. In
addition, first trough portions 25 are recessed so as to have U
shapes that curve concavely toward a radially-inner side, for
example, at portions that are positioned between respective
adjacent first claw-shaped magnetic pole portions 20 of the first
yoke portion 19.
[0050] The second pole core body 21 has: a second boss portion 22
that has an outer circumferential surface that has a cylindrical
shape, and in which a rotating shaft insertion aperture 22a is
formed so as to pass through a central axial position; a thick
ring-shaped second yoke portion 23 that is disposed so as to extend
radially outward from a second end edge portion of the second boss
portion 22; and second claw-shaped magnetic pole portions 24 that
are disposed so as to extend toward a first axial end from outer
circumferential portions of the second yoke portion 23. Eight, for
example, second claw-shaped magnetic pole portions 24 are formed so
as to have a tapered shape in which a radially-outermost surface
shape is an approximately trapezoidal shape, a circumferential
width gradually becomes narrower toward a tip end, and a radial
thickness gradually becomes thinner toward the tip end, and are
arranged on the outer circumferential portions of the second yoke
portion 23 at a uniform angular pitch circumferentially. In
addition, second trough portions 26 are recessed so as to have U
shapes that curve concavely toward a radially-inner side, for
example, at portions that are positioned between respective
adjacent first claw-shaped magnetic pole portions 24 of the second
yoke portion 23.
[0051] First and second pole core bodies 17 and 21 that are
configured in this manner are fixed to the rotating shaft 16 that
has been fitted through the rotating shaft insertion apertures 18a
and 22a such that the first and second claw-shaped magnetic pole
portions 20 and 24 alternately intermesh and a second end surface
of the first boss portion 18 is abutted to a first end surface of
the second boss portion 22. The field coil 14, which has been wound
onto a bobbin (not shown), is mounted in a space that is surrounded
by the first and second boss portions 18 and 22, the first and
second yoke portions 19 and 23, and the first and second
claw-shaped magnetic pole portions 20 and 24. Here, the first and
second boss portions 18 and 22 and the first and second yoke
portions 19 and 23 correspond to a boss portion and first and
second yoke portions of the pole core 15. Furthermore, tip end
portions of the first and second claw-shaped magnetic pole portions
20 and 24 overlap with the second and first yoke portions 23 and
19, respectively, in the axial direction.
[0052] First magnetic guidance members 30 are prepared so as to
have trapezoidal cross sections that have a predetermined thickness
using a magnetic material such as iron, or a ferromagnetic alloy,
etc., and interfitting grooves 31 are recessed into upper surfaces
so as to have openings. Here, upper and lower surfaces of the first
magnetic guidance members 30 and bottom surfaces of the
interfitting grooves 31 are parallel flat surfaces. The first
interfitting grooves 31 are formed so as to have wedge shapes in
which groove width become gradually narrower toward the openings.
First permanent magnets 32 are prepared so as to have an external
shape that conforms to an internal shape of the first interfitting
grooves 31, that is, so as to have trapezoidal cross sections in
planes that are perpendicular to a thickness direction, and so as
to have thicknesses that are similar to those of the first magnetic
guidance members 30, and upper and lower surfaces (an outer
circumferential surface and an inner circumferential surface) of
the first permanent magnets 32 are parallel flat surfaces. The
first permanent magnets 32 are fitted into the first interfitting
grooves 31 such their thickness directions are oriented in the
thickness direction of the first magnetic guidance members 30, and
first end surfaces of the first permanent magnets 32 and first end
surfaces of the first magnetic guidance members 30 are positioned
in a common plane, and are held in the first magnetic guidance
member 30 by applying an adhesive if required. Thus, the bottom
surfaces of the first interfitting grooves 31 and the lower
surfaces of the first permanent magnets 32 face each other in close
contact or so as to have minute gaps, and the first magnetic
guidance members 30 and the first permanent magnets 32 are
connected magnetically.
[0053] Second magnetic guidance members 35 are prepared into
identical shapes as the first magnetic guidance members 30 using an
identical material. Second permanent magnets 37 are prepared into
identical shapes as the first permanent magnets 32 using an
identical material. The second permanent magnets 37 are fitted into
the second interfitting grooves 36 such their thickness directions
is oriented in the thickness direction of the second magnetic
guidance members 35, and first end surfaces of the second permanent
magnets 37 and first end surfaces of the second magnetic guidance
members 35 are positioned in a common plane, and are held in the
second magnetic guidance members 35 by applying an adhesive if
required. Thus, the bottom surfaces of the second interfitting
grooves 36 and the lower surfaces of the second permanent magnets
37 face each other in close contact or so as to have minute gaps,
and the second magnetic guidance members 35 and the second
permanent magnets 37 are connected magnetically to the second
magnetic guidance members 35.
[0054] First holding grooves 27 are recessed so as to pass through
from a first end portion to a second end portion of the first yoke
portion 19 near roots of respective first claw-shaped magnetic pole
portions 20 of the first pole core body 17 so as to have openings
at respective facing portions radially outside inner walls surfaces
of the respective first trough portions 25 and so as to have groove
directions in the axial direction. Similarly, second holding
grooves 28 are recessed so as to pass through from a first end
portion to a second end portion of the second yoke portion 23 near
roots of respective second claw-shaped magnetic pole portions 24 of
the second pole core body 21 so as to have openings at respective
facing portions radially outside inner walls surfaces of the
respective second trough portions 26 and so as to have groove
directions in the axial direction. Here, the first and second
holding grooves 27 and 28 are formed by broaching, or end milling,
etc., so as to have groove shapes into which the first and second
magnetic guidance members 30 and 35 can be fitted.
[0055] The first magnetic guidance members 30 are mounted to the
first pole core body 17 by being press-fitted into the facing first
holding grooves 27 from axially outside, for example, with the
first permanent magnets 32 oriented upward so as to be magnetically
connected when disposed so as to span each of the first trough
portions 25, adhesive being applied if required. At that point, the
thickness directions of the first magnetic guidance members 30 and
the first permanent magnets 32 are oriented in the axial direction.
When viewed from a radial direction, the first permanent magnets 32
are positioned entirely in an inside diameter portion of the second
claw-shaped magnetic pole portions 24. The upper surfaces of the
first permanent magnets 32 face inner circumferential surfaces near
the tip ends of the second claw-shaped magnetic pole portions 24 so
as to leave a predetermined clearance.
[0056] Similarly, the second magnetic guidance members 35 are
mounted to the second pole core body 21 by being press-fitted into
the facing second holding grooves 28 from axially outside, for
example, with the second permanent magnets 37 oriented upward so as
to be magnetically connected when disposed so as to span each of
the second trough portions 26, adhesive being applied if required.
At that point, the thickness directions of the second magnetic
guidance members 35 and the second permanent magnets 37 are
oriented in the axial direction. When viewed from a radial
direction, the second permanent magnets 37 are positioned entirely
in an inside diameter portion of the first claw-shaped magnetic
pole portions 20. The upper surfaces of the second permanent
magnets 37 face inner circumferential surfaces near the tip ends of
the second claw-shaped magnetic pole portions 24 so as to leave a
predetermined clearance.
[0057] The first and second permanent magnets 32 and 37 are
magnetically oriented in directions of magnetization 40 that are
opposite to the orientation of a magnetic field 41 that the field
current that flows through the field coil 14 produces in a plane
that is perpendicular to a central axis of the rotor 13. In other
words, if the magnetic field 41 is generated in the direction of
the arrow shown in FIG. 1 when an electric current is passed
through the field coil 14, the first and second permanent magnets
32 and 37 are magnetically oriented in a reverse direction to the
magnetic field 41. Here, the directions of magnetization 40 of the
first and second permanent magnets 32 and 37 may be oriented
radially, and extensions of the directions of magnetization 40 are
directed at inner circumferential surfaces near the tip ends of the
facing first and second claw-shaped magnetic pole portions 20 and
24. Moreover, in the case of a design in which the orientation of
the magnetic field 41 that the field current that flows through the
field coil 14 produces is inverted, the first and second permanent
magnets 32 and 37 will also be magnetically oriented in a reverse
direction.
[0058] Next, action of an automotive alternator 1 that has been
configured in this manner will be explained.
[0059] First, current is supplied from a battery (not shown) to the
field coil 14 of the rotor 13 by means of the brushes 9 and the
slip rings 8, generating magnetic flux. The first claw-shaped
magnetic pole portions 20 of the first pole core body 17 are
magnetized into North-seeking (N) poles by this magnetic flux, and
the second claw-shaped magnetic pole portions 24 of the second pole
core body 21 are magnetized into South-seeking (S) poles.
[0060] At the same time, rotational torque from an engine is
transmitted to the shaft 16 by means of a belt (not shown) and the
pulley 6, rotating the rotor 13. Thus, a rotating magnetic field is
applied to the stator coil 12 of the stator 10, generating
electromotive forces in the stator coil 12. These
alternating-current electromotive forces are rectified into direct
current by the rectifier to charge the battery or to be supplied to
electric loads, etc.
[0061] Next, action of the magnetic flux will be explained with
reference to FIGS. 4 and 5.
[0062] First, magnetic flux 42a is generated when an electric
current is passed through the field coil 14. This magnetic flux 42a
enters tooth portions of the stator core 11 by passing through the
air gap 29 from the first claw-shaped magnetic pole portions 20.
The magnetic flux 42a then moves circumferentially through a core
back portion from the tooth portions of the stator core 11, and
enters neighboring second claw-shaped magnetic pole portions 24 by
passing through the air gap 29 from the tooth portions that face
those second claw-shaped magnetic pole portions 24. Next, the
magnetic flux 42a that has entered the second claw-shaped magnetic
pole portions 24 passes through the second yoke portion 23, the
second boss portion 22, the first boss portion 18, and the first
yoke portion 19, and reaches the first claw-shaped magnetic pole
portions 20. Now, in a conventional Lundell rotor, because the
first and second pole core bodies are at their design limit, they
are magnetically saturated by the magnetic field that is generated
by the field coil, reducing magnetic flux that is generated by the
rotor.
[0063] In Embodiment 1, the first and second permanent magnets 32
and 37 are magnetically oriented so as to be opposite to the
orientation of the magnetic field 41 that is generated by the field
coil 14. Thus, the orientation of the magnetic field that
originates from the first and second permanent magnets 32 and 37 is
in a reverse direction to the magnetic field 41 that is generated
by the field coil 14. To interlink with the stator core 11, it is
necessary for the magnetic flux 42b that originates from these
first and second permanent magnets 32 and 37 to make a round trip
across the air gap 29, which has a large magnetic resistance. The
first and second permanent magnets 32 and 37 are disposed radially
inside the second and first claw-shaped magnetic pole portions 24
and 20, and are disposed so as to circuit in a shorter magnetic
path length than the inner circumferential surface sides of the
first and second claw-shaped magnetic pole portions 20 and 24. In
addition, because the first and second permanent magnets 32 and 37
are positioned entirely in an inside diameter portion of the second
and first claw-shaped magnetic pole portions 24 and 20 when viewed
from a radial direction, the magnetic flux 42b that originates from
the second permanent magnets 37, for example, is less likely to
flow through the stator core 11. Thus, a large portion of the
magnetic flux 42b forms a closed magnetic circuit inside the rotor
without going around through the stator core 13.
[0064] Specifically, magnetic flux 42b that originates from the
first permanent magnets 32 enters the first magnetic guidance
members 30. Here, the first trough portions 25, i.e., large air
gaps, are present below the first magnetic guidance members 30.
Thus, the magnetic flux 42b that has entered the first magnetic
guidance members 30 flows through the first magnetic guidance
members 30 in two circumferential directions and enters the first
yoke portion 19, passes through the first boss portion 18, the
second boss portion 22, the second yoke portion 23, and the second
claw-shaped magnetic pole portions 24, and returns to the first
permanent magnets 37. The magnetic flux 42b that originates from
the second permanent magnets 37 enters the first claw-shaped
magnetic pole portions 20 across the air gap, passes through the
first yoke portion 19, the first boss portion 18, and the second
boss portion 22, and enters the second yoke portion 23. The
magnetic flux 42b that has entered the second yoke portion 23 flows
upward through two sides of the second trough portions 26 of the
second yoke portion 23, enters the second magnetic guidance members
35 from two ends of the second magnetic guidance members 35, and
returns to the second permanent magnets 37.
[0065] Thus, the magnetic flux 42b that originates from the first
and second permanent magnets 32 and 37 is in a reverse direction to
the magnetic flux 42a that originates from the field coil 14,
enabling the magnetic flux density of the magnetic bodies that
constitute the first and second pole core bodies 17 and 21 to be
reduced significantly, thereby enabling magnetic saturation to be
relieved.
[0066] Next, actions and effects due to disposing the magnetic
guidance members that support the permanent magnets so as to span
the trough portions will be explained with reference to FIGS. 6 and
7. FIG. 6 is an enlarged end elevation that shows a vicinity of a
magnetic flux guidance member of the rotor that is shown in FIG. 4,
and FIG. 7 is an enlarged end elevation that shows a vicinity of a
magnetic flux guidance member of a rotor that functions as a
comparative example in which trough portions are embedded in a
magnetic member.
[0067] In FIG. 6, the magnetic flux 42a that originates from the
field coil 14 passes through the first boss portion 18 and the
first yoke portion 19 and reaches the first claw-shaped magnetic
pole portions 20. Now, if the magnetic path cross-sectional area of
the first yoke portion 19 is smaller than the magnetic path
cross-sectional area of the first boss portion 18, then the first
yoke portion 19 becomes magnetically saturated, and the magnetic
flux 42a that originates from the field coil 14 cannot be used
effectively. Thus, in order to alleviate magnetic saturation in the
first yoke portion 19, it is conceivable that the magnetic path
cross-sectional area of the first yoke portion 19 could be made
approximately equivalent to the magnetic path cross-sectional area
of the first boss portion 18, as described in Patent Literature 1.
However, in that case, rotor inertia is increased because axial
dimensions of the rotor become large.
[0068] The magnetic flux 42b that originates from the first
permanent magnets 32 enters the first magnetic guidance members 30,
flows through the first magnetic guidance members 30
circumferentially, and is guided toward circumferential side
surfaces of the first yoke portion 19. The magnetic flux 42b that
is guided to the circumferential side surfaces of the first yoke
portion 19 flows radially inward through the first yoke portion 19
along the first trough portions 25, and reaches the first boss
portion 18. Here, the magnetic flux 42b flows through the first
yoke portion 19 in a reverse direction to the magnetic flux 42a,
alleviating magnetic saturation of the first yoke portion 19.
[0069] In FIG. 7, because the first permanent magnets 32 are
magnetically oriented in a reverse direction to the direction of
the magnetic field that is produced by the field coil 14, and the
first trough portions 25 are filled by the magnetic members 55, the
magnetic flux 42b that originates from the first permanent magnets
32 flows radially inward through the magnetic members 55, and flows
through the first yoke portion 19 from bottom portions of the first
trough portions 25. In other words, the magnetic flux 42b flows
toward the first boss portion 18 without passing through the
portions of the first yoke portion 19 on two circumferential sides
of the first trough portions 25. Thus, alleviation of magnetic
saturation in the first yoke portion 19 that results from the
magnetic flux 42a flowing through the first yoke portion 19 is not
performed, and in addition rotor inertia is also increased, making
belt service life deteriorate.
[0070] Thus, by adopting the present configuration, effects such as
enabling magnetic saturation to be relieved can be achieved by
enabling the magnetic flux density of the magnetic bodies that
constitute the first and second pole core bodies 17 and 21 to be
reduced significantly while suppressing increases in rotor
inertia.
[0071] Next, stator interlinked magnetic flux relative to field
magnetomotive force (field ampere turns) and generated power
relative to rotational frequency (direct current A) were measured
using an automotive alternator 1 that was configured in this
manner, and the results are shown in FIGS. 8 and 9. For comparison,
a conventional device from which the first and second permanent
magnets 32 and 37 were omitted was prepared, stator interlinked
magnetic flux relative to field magnetomotive force and generated
power relative to rotational frequency were measured, and the
results are also shown in FIGS. 8 and 9. Moreover, in FIGS. 8 and
9, a solid line represents the present invention, and a broken line
represents the conventional device.
[0072] It can be seen from FIG. 8 that the difference between the
automotive alternator 1 and the conventional device is small in a
region in which field magnetomotive force is small, and the
difference between the automotive alternator 1 and the conventional
device increases when a region in which magnetic saturation begins
is exceeded. In other words, it can be seen that disposing the
first and second permanent magnets 32 and 37 relieves magnetic
saturation, thereby increasing the amount of magnetic flux that
interlinks with the stator 10. Similarly, it can be seen from FIG.
9 that greater generated power can be obtained in the automotive
alternator 1 than in the conventional device, particularly in a low
rotational range.
[0073] In other words, in conventional devices, thirty percent or
more of the magnetomotive force of the field is expended in the
magnetic circuit of the rotor as a result of magnetic saturation,
making it difficult to increase the amount of magnetic flux. In
Embodiment 1, on the other hand, because magnetic saturation is
relieved as described above, it can be inferred that the magnetic
flux that interlinks with the stator 10 is increased, increasing
generated power. In particular, it has been confirmed that
generated power can be increased significantly in a low-speed
idling region where magnetic saturation is pronounced.
[0074] In Embodiment 1, because first and second magnetic guidance
members 30 and 35 are disposed so as to span over first and second
trough portions 25 and 26, it is not necessary to fill the first
and second trough portions 25 and 26 with the first and second
magnetic guidance members 30 and 35, enabling the volume of the
first and second magnetic guidance members 30 and 35 to be reduced.
In addition, because first and second permanent magnets 32 and 37
are held by the first and second magnetic guidance members 30 and
35 that are disposed so as to span over the first and second trough
portions 25 and 26, the first and second permanent magnets 32 and
37 can be a minimum required size. Thus, centrifugal forces that
act on the first and second magnetic guidance members 30 and 35 and
the first and second permanent magnets 32 and 37 during high-speed
rotation are reduced, and the effects of displacement of the first
and second claw-shaped magnetic pole portions 20 and 24 that result
from the centrifugal forces and thermal expansion are also
eliminated. The first and second permanent magnets 32 and 37 can
thereby be held in the pole core 15 stably using a simple holding
construction.
[0075] Because the first and second magnetic guidance members 30
and 35 link radially outer portions of inner wall surfaces of the
first and second trough portions 25 and 26 circumferentially,
occurrences of deformation of the pole core 15 can be
suppressed.
[0076] Because the first and second magnetic guidance members 30
and 35 are prepared as separate parts from the first and second
pole core bodies 17 and 21, milling precision is easily ensured,
and interfitting surfaces of the first and second holding grooves
27 and 28 and interfitting surfaces of the first and second
permanent magnets 32 and 37 can be prepared with high precision.
Thus, because gaps at interfitting portions between the first and
second magnetic guidance members 30 and 35 and the first and second
yoke portions 19 and 23, and also gaps at interfitting portions
between the first and second magnetic guidance members 30 and 35
and the first and second permanent magnets 32 and 37, can be kept
to a minimum, reducing magnetic resistance at these interfitting
portions, the amount of magnetic flux from the magnets is
increased, enabling the magnets to be used effectively.
[0077] Because the first and second permanent magnets 32 and 37 are
disposed so as to face inner circumferential surfaces near tip ends
of the second and first claw-shaped magnetic pole portions 24 and
20, the first and second permanent magnets 32 and 37 are positioned
radially inside an outermost circumferential surface of the rotor
13. Thus, stator slot harmonics are confined to outermost
circumferential portions of the first and second claw-shaped
magnetic pole portions 20 and 24, and do not act to heat the first
and second permanent magnets 32 and 37 by direct induction. As a
result, the first and second permanent magnets 32 and 37 are
prevented from being heated and thermally demagnetized.
[0078] Because the first and second permanent magnets 32 and 37 are
disposed so as to face the inner circumferential surfaces near the
tip ends of the second and first claw-shaped magnetic pole portions
24 and 20, the magnetic circuits of the first and second permanent
magnets 32 and 37 are closed magnetic circuits inside the rotor. In
addition, because the first and second permanent magnets 32 and 37
are positioned entirely in an inside diameter portion of the second
and first claw-shaped magnetic pole portions 24 and 20 when viewed
from a radial direction, magnetic flux components that interact
with the stator 10 are eliminated. Thus, the occurrence of voltages
induced by the first and second permanent magnets 32 and 37 during
no-load de-energization is suppressed. As a result, the magnet
volume of the first and second permanent magnets 32 and 37 can be
increased.
[0079] Because the first and second permanent magnets 32 and 37 are
prepared into columnar bodies that have trapezoidal cross sections
that have a predetermined thickness, the first and second permanent
magnets 32 and 37 can be cut from a magnet base material
efficiently using an abrasive wheel, increasing material yield.
[0080] Moreover, in Embodiment 1 above, first and second holding
grooves 27 and 28 are recessed so as to have groove directions that
are parallel to a central axis of a rotor 13 and so as to pass
through from a first end to a second end of first and second yoke
portions 19 and 23, but it is not absolutely necessary for first
and second holding grooves to pass through axially, provided that
they have an opening at the first end or the second end of the
first and second yoke portions 19 and 23.
[0081] In Embodiment 1 above, the first and second permanent
magnets 32 and 37 are fitted into the first and second magnetic
guidance members 30 and 35, but the holding method for the
permanent magnets is not limited to interfitting, and for example,
a joining means such as an adhesive or brazing, etc., may also be
used.
[0082] The first and second permanent magnets 32 and 37 are formed
so as to have trapezoidal cross sections that have a predetermined
thickness, but the first and second permanent magnets 32 and 37 are
not limited to a particular cross-sectional shape provided that
they are held by the first and second magnetic guidance
members.
[0083] The first and second magnetic guidance members 30 and 35 may
also be mounted by being press-fitted from axially outside or from
axially inside into the first and second holding grooves 27 and 28
of the first and second pole core bodies 17 and 21 in an integrated
state, and they may also be mounted by being press-fitted from
axially outside into the first and second holding grooves 27 and 28
of the first and second pole core bodies 17 and 21 that have been
assembled and integrated by alternately intermeshing the first and
second claw-shaped magnetic pole portions 20 and 24.
Embodiment 2
[0084] FIG. 10 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 2
of the present invention, and FIG. 11 is a perspective that
explains a method for mounting a permanent magnet to a magnetic
guidance member in the automotive alternator according to
Embodiment 2 of the present invention.
[0085] In FIGS. 10 and 11, upper surfaces of first permanent
magnets 32A are formed into flat surfaces that are approximately
parallel to inner circumferential surfaces near tip ends of second
claw-shaped magnetic pole portions 24. Directions of magnetization
40 of the first permanent magnets 32A are perpendicular to those
upper surfaces. Second permanent magnets 37 are prepared into
identical shapes as the first permanent magnets 32 using an
identical material.
[0086] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0087] In a rotor 13A that is configured in this manner, because
upper surfaces of first permanent magnets 32A are approximately
parallel to inner circumferential surfaces near tip ends of facing
second claw-shaped magnetic pole portions 24, gaps between the
first permanent magnets 32A and the second claw-shaped magnetic
pole portions 24 can be reduced. Thus, magnet magnetic flux does
not enter the second permanent magnets 32A from the inner
circumferential surfaces near the tip ends of the second
claw-shaped magnetic pole portions 24, reducing the amount of
magnetic flux that leaks. Because the first permanent magnets 32A
are magnetized in a direction that is perpendicular to their upper
surfaces, magnet magnetic flux does not enter the first permanent
magnets 32A from the inner circumferential surfaces near the tip
ends of the second claw-shaped magnetic pole portions 24, reducing
the amount of magnetic flux that leaks. In addition, by making the
upper surfaces of the first permanent magnets 32A inclined
surfaces, magnetic pole area can be used maximally, enabling the
amount of effective magnetic flux to be increased.
[0088] Although not shown, because second permanent magnets are
also configured in a similar manner to the first permanent magnets,
magnet magnetic flux does not enter inner circumferential surfaces
near tip ends of first claw-shaped magnetic pole portions 20 from
the second permanent magnets, reducing the amount of magnetic flux
that leaks, and also enabling the amount of effective magnetic flux
to be increased.
[0089] Thus, according to Embodiment 2, because the magnetic flux
that originates from the permanent magnets does not flow through
the closed magnetic circuit inside the rotor, the amount of
magnetic flux that leaks is reduced, and the amount of effective
magnetic flux is increased, output can be increased.
Embodiment 3
[0090] FIG. 12 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 3
of the present invention, and FIG. 13 is a perspective that
explains a method for mounting a permanent magnet to a magnetic
guidance member in the automotive alternator according to
Embodiment 3 of the present invention.
[0091] In FIGS. 12 and 13, first magnetic guidance members 30A are
formed such that bottom surfaces of first interfitting grooves 31A
are flat surfaces that are approximately parallel to inner
circumferential surfaces near tip ends of second claw-shaped
magnetic pole portions 24. Here, second magnet holding portions are
also configured in a similar manner to the first magnetic guidance
members 30A.
[0092] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0093] In a rotor 13B that is configured in this manner, the first
magnetic guidance members 30A are disposed so as to span over first
trough portions 25 by being fitted into first holding grooves 27,
and first permanent magnets 32 are fitted into the first
interfitting grooves 31A. Here, because the bottom surfaces of the
first interfitting grooves 31A of the first magnetic guidance
members 30A are formed into flat surfaces that are approximately
parallel to the inner circumferential surfaces near the tip ends of
the second claw-shaped magnetic pole portions 24, upper surfaces of
the first permanent magnets 32 are approximately parallel to the
inner circumferential surfaces near the tip ends of the second
claw-shaped magnetic pole portions 24, and directions of
magnetization 40 are approximately perpendicular to the inner
circumferential surfaces near the tip ends of the second
claw-shaped magnetic pole portions 24. Moreover, upper surfaces of
the second permanent magnets are also approximately parallel to
inner circumferential surfaces near tip ends of first claw-shaped
magnetic pole portions 20, and directions of magnetization 40 are
approximately perpendicular to the inner circumferential surfaces
near the tip ends of the first claw-shaped magnetic pole portions
20.
[0094] Consequently, in Embodiment 3, the magnetic flux that
originates from the permanent magnets also does not flow through
the closed magnetic circuit inside the rotor, reducing the amount
of magnetic flux that leaks, increasing the amount of effective
magnetic flux, and enabling output to be increased.
[0095] According to Embodiment 3, because bottom surfaces of
interfitting grooves of magnetic guidance members are made into
inclined surfaces, making upper surfaces of the permanent magnets
into inclined surfaces, which is a factor in cost increases, is no
longer necessary, enabling output to be increased using an
inexpensive configuration.
Embodiment 4
[0096] FIG. 14 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 4
of the present invention.
[0097] In FIG. 14, first holding grooves 27A are formed such that
groove directions thereof are approximately parallel to inner
circumferential surfaces near tip ends of second claw-shaped
magnetic pole portions 24. Here, second holding grooves are also
configured in a similar manner to the first holding grooves 27.
[0098] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0099] In a rotor 13C that is configured in this manner, first
magnetic guidance members 30 are disposed so as to span over first
trough portions 25 by being fitted into the first holding grooves
27A, and first permanent magnets 32 are fitted into first
interfitting grooves 31. Here, because the groove directions of the
first holding grooves 27A are formed approximately parallel to
inner circumferential surfaces near tip ends of second claw-shaped
magnetic pole portions 24, bottom surfaces of the first
interfitting grooves 31, that is, upper surfaces of the first
permanent magnets 32, are approximately parallel to the inner
circumferential surfaces near the tip ends of the second
claw-shaped magnetic pole portions 24, and directions of
magnetization 40 are approximately perpendicular to the inner
circumferential surfaces near the tip ends of the second
claw-shaped magnetic pole portions 24. Moreover, upper surfaces of
the second permanent magnets are also approximately parallel to
inner circumferential surfaces near tip ends of first claw-shaped
magnetic pole portions 20, and directions of magnetization 40 are
approximately perpendicular to the inner circumferential surfaces
near the tip ends of the first claw-shaped magnetic pole portions
20.
[0100] Consequently, in Embodiment 4, the magnetic flux that
originates from the permanent magnets also does not flow through
the closed magnetic circuit inside the rotor, reducing the amount
of magnetic flux that leaks, increasing the amount of effective
magnetic flux, and enabling output to be increased.
[0101] According to Embodiment 4, because the groove directions of
the holding grooves are approximately parallel to the inner
circumferential surfaces near the tip ends of the claw-shaped
magnetic pole portions, making upper surfaces of the permanent
magnets into inclined surfaces, which is a factor in cost
increases, is no longer necessary, enabling output to be increased
using an inexpensive configuration.
Embodiment 5
[0102] FIG. 15 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in an automotive
alternator according to Embodiment 5 of the present invention.
[0103] In FIG. 15, magnet protecting covers 50 are molded into
angular U-shaped cross sections that have a splayed shape that is
constituted by: a rectangular base portion 50a; and first and
second wing portions 50b and 50c that are disposed so as to extend
from two opposite sides of the base portion 50a. The magnet
protecting covers 50 are mounted onto first and second permanent
magnets 32 and 37 such that the base portions 50a are placed on
upper surfaces of the first and second permanent magnets 32 and 37,
and the first and second wing portions 50b and 50c are placed
alongside two side surfaces that are fitted into the first and
second interfitting grooves 31 and 36, and are fitted into the
first and second interfitting grooves 31 and 36 together with the
first and second permanent magnets 32 and 37.
[0104] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0105] In Embodiment 5, because the upper surfaces and two side
surfaces of the first and second permanent magnets 32 and 37 are
covered by the magnet protecting covers 50, even if the first and
second claw-shaped magnetic pole portions 20 and 24 vibrate in a
radial direction and do happen to contact the first and second
permanent magnets 32 and 37, the magnet protecting covers 50
function as a buffer layer, enabling occurrences of damage to the
first and second permanent magnets 32 and 37 to be suppressed. The
exposed surface area of the first and second permanent magnets 32
and 37 is also reduced, also suppressing damage and scattering of
the first and second permanent magnets 32 and 37.
[0106] Now, the magnet protecting covers 50 are interposed between
the first and second permanent magnets 32 and 37 and the second and
first claw-shaped magnetic pole portions 24 and 20. Thus, if the
magnet protecting covers 50 are prepared using a magnetic material,
the magnetic flux that leaves the permanent magnets flows through
the magnet protecting covers 50 and enters the magnetic guidance
members, and because a magnetic path that returns to the permanent
magnet is formed and the amount of magnetic flux entering the
facing claw-shaped magnetic pole portions is reduced, it is
necessary to increase the magnet volume of the permanent magnets.
Because of this, it is desirable to prepare the magnet protecting
covers using a nonmagnetic material, for example, a stainless alloy
or a synthetic resin.
[0107] The magnet protecting covers 50 are fixed by interposing the
first and second wing portions 50b and 50c between the side
surfaces of the first and second interfitting grooves 31 and 36 and
the side surfaces of the first and second permanent magnets 32 and
37, but the magnet protecting covers 50 may also be fixed by
brazing, etc., the first and second wing portions 50b and 50c to
the first and second magnetic guidance members 30 and 35.
Embodiment 6
[0108] FIG. 16 is a perspective that explains a method for mounting
a permanent magnet to a magnetic guidance member in an automotive
alternator according to Embodiment 6 of the present invention.
[0109] In FIG. 16, magnet protecting covers 50A include a base
portion 50a and first and second wing portions 50b and 50c, and
also third and fourth wing portions 50d and 50e that are disposed
so as to extend from two remaining opposite sides of the base
portion 50a. The magnet protecting covers 50A are mounted onto
first and second permanent magnets 32 and 37 such that the base
portions 50a are placed on upper surfaces of the first and second
permanent magnets 32 and 37, the first and second wing portions 50b
and 50c are placed alongside two side surfaces that are fitted into
the first and second interfitting grooves 31 and 36, and the third
and fourth wing portions 50d and 50e are also placed alongside two
end surfaces of the first and third permanent magnets 32 and 37 in
a thickness direction, and are fitted into the first and second
interfitting grooves 31 and 36 together with the first and second
permanent magnets 32 and 37.
[0110] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 5 above.
[0111] According to Embodiment 6, because the exposed surface area
of the first and second permanent magnets 32 and 37 is further
reduced, occurrences of damage to the first and second permanent
magnets 32 and 37 can be further suppressed.
Embodiment 7
[0112] FIG. 17 is a partially cut away perspective that explains a
method for mounting a permanent magnet to a magnetic guidance
member in an automotive alternator according to Embodiment 7 of the
present invention.
[0113] In FIG. 17, first and second permanent magnets 32 and 37 are
molded in a resin so as to be completely covered by a resin layer
51.
[0114] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 5 above.
[0115] According to Embodiment 7, because the first and second
permanent magnets 32 and 37 are entirely covered by the resin layer
51, occurrences of damage to the first and second permanent magnets
32 and 37 can be further suppressed.
Embodiment 8
[0116] FIG. 18 is an end elevation that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 8
of the present invention.
[0117] In FIG. 18, pairs of bracing portions 52 are disposed so as
to project from facing portions radially outside inner wall
surfaces of first trough portions 25. First magnetic guidance
members 30 are fixed to the inner wall surfaces of the first trough
portions 25 using an adhesive, etc., and are disposed so as to span
over the first trough portions 25 such that upper surfaces thereof
are placed in contact with the bracing portions 52, and two
circumferential side surfaces thereof are disposed on radially
outer sides of the first trough portions 25. Here, bracing portions
are also disposed so as to project from second trough portions, and
second magnetic guidance members are disposed so as to span in a
similar manner.
[0118] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0119] In Embodiment 8, because the first magnetic guidance members
30 are disposed so as to span over the first trough portions 25,
the volume of the first magnetic guidance members 30 can be
reduced. Thus, centrifugal forces that act on the first magnetic
guidance members 30 can be reduced, and effects of displacement of
the second claw-shaped magnetic pole portions 24 are also
eliminated. The centrifugal forces that act on the first magnetic
guidance members 30 are borne by a fixing force from the adhesive,
etc., and also by the bracing portions 52. Moreover, the same also
applies to the second magnetic guidance members.
[0120] Thus, in Embodiment 8, first and second permanent magnets
can also be held in a pole core stably using a simple holding
construction. Because the first magnetic guidance members 30 are
disposed so as to span the first trough portions 25 so as to be
linked to the first yoke portion 19 magnetically, magnetic flux
that originates in the first permanent magnets 32 can be guided
circumferentially and made to flow to the first yoke portion 19,
enabling magnetic saturation in the first yoke portion 19 to be
alleviated.
Embodiment 9
[0121] FIG. 19 is an end elevation that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 9
of the present invention.
[0122] In FIG. 19, first magnetic guidance members 30 are disposed
on radially outer portions of first trough portions 25, and are
disposed so as to span over the first trough portions 25 such that
two circumferential side surfaces thereof are fixed to inner wall
surfaces of the first trough portions 25 using an adhesive,
brazing, etc. Here, second magnetic guidance members are also
disposed so as to span in a similar manner.
[0123] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0124] In Embodiment 9, because the first magnetic guidance members
30 are disposed so as to span over the first trough portions 25,
the volume of the first magnetic guidance members 30 can be
reduced. Thus, centrifugal forces that act on the first magnetic
guidance members 30 can be reduced, and effects of displacement of
the second claw-shaped magnetic pole portions 24 are also
eliminated. The centrifugal forces that act on the first magnetic
guidance members 30 are borne by a fixing force from the adhesive,
brazing, etc. Moreover, the same also applies to the second
magnetic guidance members.
[0125] Thus, in Embodiment 9, first and second permanent magnets
can also be held in a pole core stably using a simple holding
construction. Because the first magnetic guidance members 30 are
disposed so as to span the first trough portions 25 so as to be
linked to the first yoke portion 19 magnetically, magnetic flux
that originates in the first permanent magnets 32 can be guided
circumferentially and made to flow to the first yoke portion 19,
enabling magnetic saturation in the first yoke portion 19 to be
alleviated.
Embodiment 10
[0126] FIG. 20 is a cross section that schematically shows an
automotive alternator according to Embodiment 10 of the present
invention, FIG. 21 is a perspective that shows a rotor that can be
used in the automotive alternator according to Embodiment 10 of the
present invention, FIG. 22 is a perspective that explains a method
for mounting a permanent magnet to a magnetic guidance member in
the automotive alternator according to Embodiment 10 of the present
invention, and FIGS. 23 and 24 are each cross sections that show
parts of the rotor that can be used in the automotive alternator
according to Embodiment 10 of the present invention.
[0127] In FIGS. 20 through 24, an automotive alternator 100
includes: a case 4 that is constituted by a front bracket 2 and a
rear bracket 3 that are each made of aluminum in an approximate cup
shape; a rotor 13D that is rotatably disposed inside the case 4
such that a rotating shaft 16 is supported by means of bearings 5
in the case 4; a pulley 6 that is fixed to an end portion of the
rotating shaft 16 that projects outward at a front end of the case
4; fans 7 that are fixed to two end surfaces in an axial direction
of the rotor 13D (hereinafter "axial direction"); a stator 10 that
is fixed to the case 4 so as to surround an outer circumference of
the rotor 13D so as to have a constant air gap 29 relative to the
rotor 13D; a pair of slip rings 8 that are fixed to a rear end of
the rotating shaft 16, and that supply current to the rotor 13D;
and a pair of brushes 9 that are disposed inside the case 4 so as
to slide on the respective slip rings 8. Moreover, although not
shown, a rectifier that rectifies an alternating current that is
generated in the stator 10 into direct current, and a voltage
regulator that adjusts magnitude of an alternating voltage
generated in the stator 10, etc., are disposed inside the case
4.
[0128] The stator 10 includes: a cylindrical stator core 11; and a
stator coil 12 that is mounted to the stator core 11, and in which
an alternating current arises due to changes in magnetic flux from
a field coil 14 (described below) that accompany rotation of the
rotor 13D.
[0129] The rotor 13D includes: a field coil 14 that generates
magnetic flux on passage of an excitation current; a pole core 15
that is disposed so as to cover the field coil 14 and in which
magnetic poles are formed by that magnetic flux; and the rotating
shaft 16, which is fitted through a central axial position of the
pole core 15.
[0130] The pole core 15 is configured so as to be divided into
first and second pole core bodies 17 and 21 that are each prepared
by a cold forging manufacturing method using a low carbon steel
such as S10C, for example.
[0131] The first pole core body 17 has: a first boss portion 18
that has an outer circumferential surface that has a cylindrical
shape, and in which a rotating shaft insertion aperture 18a is
formed so as to pass through a central axial position; a thick
ring-shaped first yoke portion 19 that is disposed so as to extend
radially outward from a first end edge portion of the first boss
portion 18; and first claw-shaped magnetic pole portions 20 that
are disposed so as to extend toward a second axial end from outer
circumferential portions of the first yoke portion 19. Eight, for
example, first claw-shaped magnetic pole portions 20 are formed so
as to have a tapered shape in which a radially-outermost surface
shape is an approximately trapezoidal shape, a circumferential
width gradually becomes narrower toward a tip end, and a radial
thickness gradually becomes thinner toward the tip end, and are
arranged on the outer circumferential portions of the first yoke
portion 19 at a uniform angular pitch circumferentially. In
addition, first trough portions 25 are recessed so as to have U
shapes that curve concavely toward a radially-inner side at
portions that are positioned between respective adjacent first
claw-shaped magnetic pole portions 20 of the first yoke portion
19.
[0132] The second pole core body 21 has: a second boss portion 22
that has an outer circumferential surface that has a cylindrical
shape, and in which a rotating shaft insertion aperture 22a is
formed so as to pass through a central axial position; a thick
ring-shaped second yoke portion 23 that is disposed so as to extend
radially outward from a second end edge portion of the second boss
portion 22; and second claw-shaped magnetic pole portions 24 that
are disposed so as to extend toward a first axial end from outer
circumferential portions of the second yoke portion 23. Eight, for
example, second claw-shaped magnetic pole portions 24 are formed so
as to have a tapered shape in which a radially-outermost surface
shape is an approximately trapezoidal shape, a circumferential
width gradually becomes narrower toward a tip end, and a radial
thickness gradually becomes thinner toward the tip end, and are
arranged on the outer circumferential portions of the second yoke
portion 23 at a uniform angular pitch circumferentially. In
addition, second trough portions 26 are recessed so as to have U
shapes that curve concavely toward a radially-inner side at
portions that are positioned between respective adjacent first
claw-shaped magnetic pole portions 24 of the second yoke portion
23.
[0133] Now, the first and second pole core bodies 17 and 21 are
prepared by forming a core body that has a shape in which portions
that correspond to claw-shaped magnetic pole portions project
radially outward from a yoke portion using a cold forging method,
and then bending approximately at right angles the portions that
correspond to claw-shaped magnetic pole portions that extend
radially outward from the yoke portion. First bending lines 72 when
bending and shaping the first claw-shaped magnetic pole portions 20
are formed so as to extend radially on boundaries between the first
yoke portion 19 and the first claw-shaped magnetic pole portions
20. Second bending lines 73 when bending and shaping the second
claw-shaped magnetic pole portions 24 are formed so as to extend
radially on boundaries between the second yoke portion 23 and the
second claw-shaped magnetic pole portions 24.
[0134] First and second pole core bodies 17 and 21 that are
configured in this manner are fixed to the rotating shaft 16 that
has been fitted through the rotating shaft insertion apertures 18a
and 22a such that the first and second claw-shaped magnetic pole
portions 20 and 24 alternately intermesh and a second end surface
of the first boss portion 18 is abutted to a first end surface of
the second boss portion 22. The field coil 14, which has been wound
onto a bobbin (not shown), is mounted in a space that is surrounded
by the first and second boss portions 18 and 22, the first and
second yoke portions 19 and 23, and the first and second
claw-shaped magnetic pole portions 20 and 24. Here, the first and
second boss portions 18 and 22 and the first and second yoke
portions 19 and 23 correspond to a boss portion and first and
second yoke portions of the pole core 15. Furthermore, tip end
portions of the first and second claw-shaped magnetic pole portions
20 and 24 overlap with the second and first yoke portions 23 and
19, respectively, in the axial direction.
[0135] First magnetic guidance members 60 are prepared so as to
have trapezoidal cross sections that have a predetermined thickness
using a magnetic material such as iron, or a ferromagnetic alloy,
etc. Interfitting grooves 61 that have groove directions in a
thickness direction of the first magnetic guidance members 60 are
recessed into upper surfaces of the first magnetic guidance members
60 so as to have openings. Here, upper and lower surfaces of the
first magnetic guidance members 60 and bottom surfaces of the
interfitting grooves 61 are mutually parallel flat surfaces. The
first interfitting grooves 61 are formed so as to have wedge shapes
in which groove widths become gradually narrower toward the
openings. First permanent magnets 62 are prepared so as to have
external shapes that conform to internal shapes of the first
interfitting grooves 61, that is, so as to have trapezoidal cross
sections in planes that are perpendicular to a thickness direction,
and so as to have a thickness that is thinner than that of the
first magnetic guidance members 60, and upper and lower surfaces
(an outer circumferential surface and an inner circumferential
surface) of the first permanent magnets 62 are mutually parallel
flat surfaces. The first permanent magnets 62 are fitted into the
first interfitting grooves 61 such that their thickness directions
are oriented in the thickness direction of the first magnetic
guidance members 60, and first end surfaces of the first permanent
magnets 62 and first end surfaces of the first magnetic guidance
members 60 are positioned in a common plane, and are held in the
first magnetic guidance members 60 by applying an adhesive if
required. Thus, the bottom surfaces of the first interfitting
grooves 61 and the lower surfaces of the first permanent magnets 62
face each other in close contact or so as to have minute gaps, and
the first magnetic guidance members 60 and the first permanent
magnets 62 are connected magnetically.
[0136] Second magnetic guidance members 65 are prepared into
identical shapes as the first magnetic guidance members 60 using an
identical material. Second permanent magnets 67 are prepared into
identical shapes as the first permanent magnets 62 using an
identical material. The second permanent magnets 67 are fitted into
the second interfitting grooves 66 such that their thickness
directions are oriented in the thickness direction of the second
magnetic guidance members 65, and first end surfaces of the second
permanent magnets 67 and first end surfaces of the second magnetic
guidance members 65 are positioned in a common plane, and are held
in the second magnetic guidance members 65 by applying an adhesive
if required. Thus, the bottom surfaces of the second interfitting
grooves 66 and the lower surfaces of the second permanent magnets
67 face each other in close contact or so as to have minute gaps,
and the second magnetic guidance members 65 and the second
permanent magnets 67 are connected magnetically.
[0137] First holding grooves 70 are recessed so as to reach from a
first end toward a second end portion of the first yoke portion 19
to the first bending lines 72 near roots of respective first
claw-shaped magnetic pole portions 20 of the first pole core body
17 so as to have openings at respective facing portions radially
outside inner walls surfaces of the respective first trough
portions 25 and so as to have groove directions in the axial
direction. Similarly, second holding grooves 71 are recessed so as
to reach from a second end toward a first end portion of the second
yoke portion 23 to the second bending lines 73 near roots of
respective second claw-shaped magnetic pole portions 24 of the
second pole core body 21 so as to have openings at respective
facing portions radially outside inner walls surfaces of the
respective second trough portions 26 and so as to have groove
directions in the axial direction. Here, the first and second
holding grooves 70 and 71 are formed by broaching, or end milling,
etc., so as to have groove shapes into which two side portions of
the first and second magnetic guidance members 60 and 65 can be
fitted.
[0138] The first magnetic guidance members 60 are mounted to the
first pole core body 17 by being press-fitted into the facing first
holding grooves 70 from axially outside with the first permanent
magnets 62 oriented upward so as to be magnetically connected when
disposed so as to span each of the first trough portions 25,
adhesive being applied if required. At that point, the thickness
directions of the first magnetic guidance members 60 and the first
permanent magnets 62 are oriented in the axial direction. The first
interfitting grooves 61 have openings in directions that are
positioned radially outside the first magnetic guidance members 60
that are fitted into and held by the first holding grooves 70.
[0139] The first permanent magnets 62 are held in the first
magnetic guidance members 60 such that centers thereof are shifted
toward the field coil 14 relative to centers of the first magnetic
guidance members 60 in the thickness direction, that is, offset
axially toward the field coil 14. Ends of the first permanent
magnets 62 near the field coil 14 overlap with the second
claw-shaped magnetic pole portions 24 in the axial direction, and
opposite ends of the first permanent magnets 62 from the field coil
14 do not overlap with the second claw-shaped magnetic pole
portions 24. When viewed from radially outside, portions of the
first permanent magnets 62 are exposed from the second claw-shaped
magnetic pole portions 24, and remaining portions are positioned in
an inside diameter portion of the second claw-shaped magnetic pole
portions 24, and upper surfaces thereof face inner circumferential
surfaces near the tip ends of the second claw-shaped magnetic pole
portions 24 so as to leave a predetermined clearance. Bottom
surfaces of the first interfitting grooves 61 and lower surfaces of
the first permanent magnets 62 are formed into flat surfaces that
are tangential to a cylindrical surface that is coaxial with the
rotor 13D. Cross sections of the first permanent magnets 62 in
planes that include the central axis of the rotor 13D are
rectangular. Moreover, centers of the permanent magnets are
portions that constitute centers between the upper surfaces and the
lower surfaces of the permanent magnets and centers in the
thickness direction.
[0140] The second magnetic guidance members 65 are mounted to the
second pole core body 21 by being press-fitted into the facing
second holding grooves 71 from axially outside with the second
permanent magnets 67 oriented upward so as to be magnetically
connected when disposed so as to span each of the second trough
portions 26, adhesive being applied if required. At that point, the
thickness directions of the second magnetic guidance members 65 and
the second permanent magnets 67 are oriented in the axial
direction. The second interfitting grooves 66 have openings in
directions that are positioned radially outside the second magnetic
guidance members 65 that are fitted into and held by the second
holding grooves 71.
[0141] The second permanent magnets 67 are held in the second
magnetic guidance members 65 such that centers thereof are shifted
toward the field coil 14 relative to centers of the second magnetic
guidance members 65 in the thickness direction, that is, offset
axially toward the field coil 14. Ends of the second permanent
magnets 67 near the field coil 14 overlap with the first
claw-shaped magnetic pole portions 20 in the axial direction, and
opposite ends of the second permanent magnets 67 from the field
coil 14 do not overlap with the first claw-shaped magnetic pole
portions 20. When viewed from radially outside, portions of the
second permanent magnets 67 are exposed from the first claw-shaped
magnetic pole portions 20, and remaining portions are positioned at
an inside diameter portion of the first claw-shaped magnetic pole
portions 20, and upper surfaces thereof face inner circumferential
surfaces near the tip ends of the first claw-shaped magnetic pole
portions 20 so as to leave a predetermined clearance. Bottom
surfaces of the second interfitting grooves 66 and lower surfaces
of the second permanent magnets 67 are formed into flat surfaces
that are tangential to a cylindrical surface that is coaxial with
the rotor 13D. Cross sections of the second permanent magnets 67 in
planes that include the central axis of the rotor 13D are
rectangular.
[0142] The first permanent magnets 62 are magnetically oriented
such that directions of magnetization 40 are inclined so as to have
gradients that ascend toward the field coil 14 in planes that
include the central axis of the rotor 13D and that pass through the
centers of the first permanent magnets 62. Extensions of the
directions of magnetization 40 that pass through the centers of the
first permanent magnets 62 are oriented toward the inner
circumferential surfaces near the tip ends of the facing second
claw-shaped magnetic pole portions 24. Similarly, the second
permanent magnets 67 are magnetically oriented such that directions
of magnetization 40 are inclined so as to have gradients that
ascend toward the field coil 14 in planes that include the central
axis of the rotor 13D and that pass through the centers of the
second permanent magnets 67. Extensions of the directions of
magnetization 40 that pass through the centers of the second
permanent magnets 67 are oriented toward the inner circumferential
surfaces near the tip ends of the facing first claw-shaped magnetic
pole portions 20. If the magnetic field 41 is generated in the
direction of the arrow shown in FIG. 20 when an electric current is
passed through the field coil 14, the first and second permanent
magnets 62 and 67 are magnetically oriented in a reverse direction
to the magnetic field 41. Moreover, in the case of a design in
which the orientation of the magnetic field 41 that the field
current that flows through the field coil 14 produces is inverted,
the first and second permanent magnets 62 and 67 will also be
magnetically oriented in a reverse direction.
[0143] Next, action of an automotive alternator 100 that has been
configured in this manner will be explained.
[0144] First, current is supplied from a battery (not shown) to the
field coil 14 of the rotor 13D by means of the brushes 9 and the
slip rings 8, generating magnetic flux. The first claw-shaped
magnetic pole portions 20 of the first pole core body 17 are
magnetized into North-seeking (N) poles by this magnetic flux, and
the second claw-shaped magnetic pole portions 24 of the second pole
core body 21 are magnetized into South-seeking (S) poles.
[0145] At the same time, rotational torque from an engine is
transmitted to the shaft 16 by means of a belt (not shown) and the
pulley 6, rotating the rotor 13D. Thus, a rotating magnetic field
is applied to the stator coil 12 of the stator 10, generating
electromotive forces in the stator coil 12. These
alternating-current electromotive forces are rectified into direct
current by the rectifier to charge the battery or to be supplied to
electric loads, etc.
[0146] Next, action of the magnetic flux will be explained with
reference to FIGS. 25 and 26.
[0147] First, magnetic flux 42a is generated when an electric
current is passed through the field coil 14. This magnetic flux 42a
enters tooth portions of the stator core 11 by passing through the
air gap 29 from the first claw-shaped magnetic pole portions 20.
The magnetic flux 42a then moves circumferentially through a core
back portion from the tooth portions of the stator core 11, and
enters neighboring second claw-shaped magnetic pole portions 24 by
passing through the air gap 29 from the tooth portions that face
those second claw-shaped magnetic pole portions 24. Next, the
magnetic flux 42a that has entered the second claw-shaped magnetic
pole portions 24 passes through the second yoke portion 23, the
second boss portion 22, the first boss portion 18, and the first
yoke portion 19, and reaches the first claw-shaped magnetic pole
portions 20. Now, in a conventional Lundell rotor, because the
first and second pole core bodies are at their design limit, they
are magnetically saturated by the magnetic field that is generated
by the field coil, reducing magnetic flux that is generated by the
rotor.
[0148] In Embodiment 10, the first and second permanent magnets 62
and 67 are magnetically oriented so as to be opposite to the
orientation of the magnetic field 41 that is generated by the field
coil 14. Thus, the orientation of the magnetic field that
originates from the first and second permanent magnets 62 and 67 is
in a reverse direction to the magnetic field 41 that is generated
by the field coil 14. To interlink with the stator core 11, it is
necessary for the magnetic flux 42b that originates from these
first and second permanent magnets 62 and 67 to make a round trip
across the air gap 29, which has a large magnetic resistance. The
first and second permanent magnets 62 and 67 are disposed radially
inside the second and first claw-shaped magnetic pole portions 24
and 20, and are disposed so as to circuit in a shorter magnetic
path length than the inner circumferential surface sides of the
first and second claw-shaped magnetic pole portions 20 and 24.
[0149] Because portions of the first and second permanent magnets
62 and 67 are exposed from the second and first claw-shaped
magnetic pole portions 24 and 20 when viewed from radially outside,
a portion of the magnetic flux 42b that originates from the second
permanent magnets 67, for example, can easily flow through the
stator core 11 from the portions that are exposed from the first
claw-shaped magnetic pole portions 20. In Embodiment 10, because
extensions of the directions of magnetization 40 that pass through
the centers of the second permanent magnets 67 are oriented toward
the inner circumferential surfaces near the tip ends of the facing
first claw-shaped magnetic pole portions 24, the magnetic flux 42b
flows toward the inner circumferential surfaces near the tip ends
of the first claw-shaped magnetic pole portions 20 even at the
portions that are exposed from the first claw-shaped magnetic pole
portions 20, reducing the amount of magnetic flux that flows to the
stator core 11. Thus, a large portion of the magnetic flux 42b
forms a closed magnetic circuit inside the rotor without going
around through the stator core 13D.
[0150] Specifically, magnetic flux 42b that originates from the
first permanent magnets 62 enters the first magnetic guidance
members 60. Here, the first trough portions 25, i.e., large air
gaps, are present below the first magnetic guidance members 60.
Thus, the magnetic flux 42b that has entered the first magnetic
guidance members 60 flows through the first magnetic guidance
members 60 in two circumferential directions and enters the first
yoke portion 19, passes through the first boss portion 18, the
second boss portion 22, the second yoke portion 23, and the second
claw-shaped magnetic pole portions 24, and returns to the first
permanent magnets 67 via the air gap. The magnetic flux 42b that
originates from the second permanent magnets 67 enters the first
claw-shaped magnetic pole portions 20 across the air gap, passes
through the first yoke portion 19, the first boss portion 18, and
the second boss portion 22, and enters the second yoke portion 23.
The magnetic flux 42b that has entered the second yoke portion 23
flows radially outward through two sides of the second trough
portions 26 of the second yoke portion 23, enters the second
magnetic guidance members 65 from two ends of the second magnetic
guidance members 65, and returns to the second permanent magnets
67.
[0151] Thus, the magnetic flux 42b that originates from the first
and second permanent magnets 62 and 67 is in a reverse direction
from the magnetic flux 42a that originates from the field coil 14,
enabling the magnetic flux density of the magnetic bodies that
constitute the first and second pole core bodies 17 and 21 to be
reduced significantly, thereby enabling magnetic saturation to be
relieved.
[0152] Next, no-load stator interlinked magnetic flux relative to
field magnetomotive force (field ampere turns) and generated power
relative to rotational frequency (direct current A) were measured
using an automotive alternator 100 that was configured in this
manner, and the results are shown in FIGS. 27 and 28. For
comparison, a conventional device from which the first and second
permanent magnets 62 and 67 were omitted was prepared, no-load
stator interlinked magnetic flux relative to field magnetomotive
force and generated power relative to rotational frequency were
measured, and the results are also shown in FIGS. 27 and 28.
Moreover, in FIGS. 27 and 28, a solid line represents the present
invention, and a broken line represents the conventional
device.
[0153] It can be seen from FIG. 27 that the difference between the
automotive alternator 100 and the conventional device is small in a
region in which field magnetomotive force is small, and the
difference between the automotive alternator 100 and the
conventional device increases when a region in which magnetic
saturation begins is exceeded. In other words, it can be seen that
disposing the first and second permanent magnets 62 and 67 relieves
magnetic saturation, thereby increasing the amount of magnetic flux
that interlinks with the stator 10. Similarly, it can be seen from
FIG. 28 that greater generated power can be obtained in the
automotive alternator 100 than in the conventional device,
particularly in a low rotational range.
[0154] In other words, in conventional devices, thirty percent or
more of the magnetomotive force of the field is expended in the
magnetic circuit of the rotor as a result of magnetic saturation,
making it difficult to increase the amount of magnetic flux. In
Embodiment 10, on the other hand, because magnetic saturation is
relieved as described above, it can be inferred that the magnetic
flux that interlinks with the stator 10 is increased, increasing
generated power. In particular, it has been confirmed that
generated power can be increased significantly in a low-speed
idling region where magnetic saturation is pronounced.
[0155] In Embodiment 10, because first and second magnetic guidance
members 60 and 65 are disposed so as to span over first and second
trough portions 25 and 26, it is not necessary to fill the first
and second trough portions 25 and 26 with the first and second
magnetic guidance members 60 and 65, enabling the volume of the
first and second magnetic guidance members 60 and 65 to be reduced.
In addition, because first and second permanent magnets 62 and 67
are held by the first and second magnetic guidance members 60 and
65 that are disposed so as to span over the first and second trough
portions 25 and 26, the first and second permanent magnets 62 and
67 can be a minimum required size. Thus, centrifugal forces that
act on the first and second magnetic guidance members 60 and 65 and
the first and second permanent magnets 62 and 67 during high-speed
rotation are reduced, and the effects of displacement of the first
and second claw-shaped magnetic pole portions 20 and 24 that result
from the centrifugal forces and thermal expansion are also
eliminated. The first and second permanent magnets 62 and 67 can
thereby be held in the pole core 15 stably using a simple holding
construction.
[0156] Because the first and second magnetic guidance members 60
and 65 link radially outer portions of inner wall surfaces of the
first and second trough portions 25 and 26 circumferentially,
occurrences of deformation of the pole core 15 can be
suppressed.
[0157] Because the first and second magnetic guidance members 60
and 65 are prepared as separate parts from the first and second
pole core bodies 17 and 21, milling precision is easily ensured,
interfitting surfaces of the first and second holding grooves 70
and 71 and interfitting surfaces of the first and second permanent
magnets 62 and 67 can be prepared with high precision. Thus,
because gaps at interfitting portions between the first and second
magnetic guidance members 60 and 65 and the first and second yoke
portions 19 and 23, and also gaps at interfitting portions between
the first and second magnetic guidance members 60 and 65 and the
first and second permanent magnets 62 and 67, can kept to a
minimum, reducing magnetic resistance at these interfitting
portions, the amount of magnetic flux from the magnets is
increased, enabling the magnets to be used effectively.
[0158] Because the first and second permanent magnets 62 and 67 are
positioned radially inside outermost circumferential surfaces of
the rotor 13D, stator slot harmonics are confined to outermost
circumferential surface portions of the first and second
claw-shaped magnetic pole portions 20 and 24, and do not act to
heat the first and second permanent magnets 62 and 67 by induction
directly. As a result, the first and second permanent magnets 62
and 67 are prevented from being heated and thermally
demagnetized.
[0159] Extensions of the directions of magnetization 40 that pass
through the centers of the first and second permanent magnets 62
and 67 are oriented toward inner circumferential surfaces near tip
ends of facing second and first claw-shaped magnetic pole portions
24 and 20. Thus, the magnetic circuits of the first and second
permanent magnets 62 and 67 are closed magnetic circuits inside the
rotor, reducing magnetic flux components that interact with the
stator 10. Thus, the occurrence of voltages induced by the first
and second permanent magnets 62 and 67 during no-load
de-energization is suppressed. Even if the amount of exposure of
the first and second permanent magnets 62 and 67 from the second
and first claw-shaped magnetic pole portions 24 and 20 when viewed
from a radial direction is increased, increases in magnetic flux
components that interact with the stator 10 can be suppressed. As a
result of the above, the magnet volume of the first and second
permanent magnets 62 and 67 can be increased.
[0160] Because the first and second permanent magnets 62 and 67 are
held in the first and second magnetic guidance members 60 and 65 so
as to be offset axially, portions of the first and second permanent
magnets 62 and 67 that face the inner circumferential surfaces near
the tip ends of the second and first claw-shaped magnetic pole
portions 24 and 20 can be increased. As a result, leakage of
magnetic flux 42b that originates from the first and second
permanent magnets 62 and 67 can be reduced.
[0161] Because the first and second magnetic guidance members 60
and 65 are prepared so as to be thicker than the thickness of the
first and second permanent magnets 62 and 67, interfitting surface
area between the first and second magnetic guidance members 60 and
65 and the first and second holding grooves 70 and 71 can be
increased. As a result, holding strength on the first and second
magnetic guidance members 60 and 65 by the first and second yoke
portions 19 and 23 is increased, enabling the first and second
permanent magnets 62 and 67 to be held stably even if the
centrifugal forces act on the first and second permanent magnets 62
and 67 and the first and second magnetic guidance members 60 and
65.
[0162] Now, the first and second bending lines 72 and 73 are formed
on boundaries between the first and second yoke portions 19 and 23
and the first and second claw-shaped magnetic pole portions 20 and
24. The circumferential widths of the first and second claw-shaped
magnetic pole portions 20 and 24 are gradually reduced toward the
tip end portions from the bending lines 72 and 73. Thus, if the
first and second holding grooves 70 and 71 are formed axially
outside the first and second bending lines 72 and 73, the further
outside the bending lines 72 and 73 the smaller the interfitting
surface area between the first and second holding grooves 70 and 71
and the first and second magnetic guidance members 60 and 65.
Because of this, it is preferable not to form the first and second
holding grooves 70 and 71 axially outside the first and second
bending lines 72 and 73. Alternatively, if the first and second
holding grooves 70 and 71 are formed so as to pass through axially,
it is preferable to fit the first and second magnetic guidance
members 60 and 65 into the first and second holding grooves 70 and
71 so as not to be positioned on a field coil 14 side of the
bending lines 72 and 73.
[0163] Thus, it is preferable for the first and second magnetic
guidance members 60 and 65 to be fitted into and held by the first
and second holding grooves 70 and 71 so as to be positioned between
points of intersection O between the first and second holding
grooves 70 and 71 and the first and second bending lines 72 and 73,
and axial outer end surfaces of the first and second yoke portions
19 and 23.
[0164] Moreover, the first and second permanent magnets 62 and 67
are formed so as to have trapezoidal cross sections that have a
predetermined thickness, but the first and second permanent magnets
62 and 67 are not limited to a particular cross-sectional shape
provided that they can be fitted into and held by the first and
second magnetic guidance members 60 and 65. Similarly, the first
and second magnetic guidance members 60 and 65 are formed so as to
have trapezoidal cross sections that have a predetermined
thickness, but the first and second magnetic guidance members 60
and 65 are not limited to a particular cross-sectional shape
provided that they can be fitted into and held by the first and
second holding grooves 70 and 71. In other words, groove shapes of
the interfitting grooves and the holding grooves can be set
arbitrarily to match the shapes of the permanent magnets and the
interfitting portions of the magnetic guidance members.
[0165] Cross sections of the first and second permanent magnets 62
and 67 in planes that include the central axis of the rotor 13D are
formed so as to have a rectangular shape, but that cross-sectional
shape can also be set arbitrarily.
Embodiment 11
[0166] Embodiment 11 is configured in a similar manner to
Embodiment 10 above except that bending lines are formed at
boundaries between claw-shaped magnetic pole portions and yoke
portions so as to be inclined so as to have gradients that descend
toward a field coil 14. Moreover, because first and second
permanent magnets 62 and 67 are held in a similar manner by first
and second pole core bodies 17 and 21, only a holding construction
for the second permanent magnets 67 will be explained here, and
explanation of a holding construction for the first permanent
magnets 62 will be omitted.
[0167] FIG. 29 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 11
of the present invention.
[0168] In FIG. 29, second bending lines 73a are formed at
boundaries between second claw-shaped magnetic pole portions 24 and
a second yoke portion 23 so as to be inclined so as to have
gradients that descend toward the field coil 14.
[0169] Second holding grooves 71 are recessed so as to reach from a
second end toward a first end portion of the second yoke portion 23
to the second bending lines 73 near roots of respective second
claw-shaped magnetic pole portions 24 of the second pole core body
21 so as to have openings at respective facing portions radially
outside inner walls surfaces of respective second trough portions
26 and so as to have groove directions in the axial direction.
Second magnetic guidance members 65 are mounted to the second pole
core body 21 by being press-fitted into the facing second holding
grooves 71 from axially outside with the second permanent magnets
67 oriented upward so as to be magnetically connected when disposed
so as to span each of the second trough portions 26, adhesive being
applied if required.
[0170] Here, thickness directions of the second magnetic guidance
members 65 and the second permanent magnets 67 are oriented in the
axial direction. The second permanent magnets 67 are held in the
second magnetic guidance members 65 such that centers thereof are
shifted toward the field coil 14 relative to centers of the second
magnetic guidance members 65 in the thickness direction, that is,
offset axially toward the field coil 14. Ends of the second
permanent magnets 67 near the field coil 14 overlap with the first
claw-shaped magnetic pole portions 20 in the axial direction, and
opposite ends of the second permanent magnets 67 from the field
coil 14 do not overlap with the first claw-shaped magnetic pole
portions 20. When viewed from radially outside, portions of the
second permanent magnets 67 are exposed from the first claw-shaped
magnetic pole portions 20, and remaining portions are positioned at
an inside diameter portion of the first claw-shaped magnetic pole
portions 20, and upper surfaces thereof face inner circumferential
surfaces near the tip ends of the first claw-shaped magnetic pole
portions 20 so as to leave a predetermined clearance.
[0171] The second permanent magnets 67 are magnetically oriented
such that directions of magnetization 40 are inclined so as to have
gradients that ascend toward the field coil 14 in planes that
include the central axis of the rotor 13D and that pass through the
centers of the second permanent magnets 67. Extensions of the
directions of magnetization 40 that pass through the centers of the
second permanent magnets 67 are oriented toward the inner
circumferential surfaces near the tip ends of the facing first
claw-shaped magnetic pole portions 20.
[0172] Consequently, in Embodiment 11, effects can also be achieved
in a similar manner to Embodiment 10.
[0173] Now, if the second holding grooves 71 are formed axially
outside the second bending lines 73a, the further outside the
second bending lines 73a the smaller the interfitting surface area
between the second holding grooves 71 and the second magnetic
guidance members 65. Because of this, it is preferable not to form
the second holding grooves 71 axially outside second bending lines
73a. Alternatively, if the second holding grooves 71 are formed so
as to pass through axially, it is preferable to fit the second
magnetic guidance members 65 into the second holding grooves 71 so
as not to be positioned on a field coil 14 side of the second
bending lines 73a.
[0174] Thus, in Embodiment 11, it is also preferable for the second
magnetic guidance members 65 to be fitted into and held in the
second holding grooves 71 so as to be positioned between points of
intersection O between the second holding grooves 71 and second
bending lines 73a, and axial outer end surfaces of the first and
second yoke portions 19 and 23.
Embodiment 12
[0175] Embodiment 12 is configured in a similar manner to
Embodiment 10 above except that permanent magnets are used in which
a direction of magnetization is perpendicular to a lower surface of
the permanent magnet. Moreover, because first and second permanent
magnets 62 and 67 are held in a similar manner by first and second
pole core bodies 17 and 21, only a holding construction for the
second permanent magnets 67 will be explained here, and explanation
of a holding construction for the first permanent magnets 62 will
be omitted.
[0176] FIG. 30 is a cross section that shows part of a rotor that
can be used in an automotive alternator according to Embodiment 12
of the present invention.
[0177] In FIG. 30, second magnetic guidance members 65A are
prepared so as to have trapezoidal cross sections that have a
predetermined thickness using a magnetic material such as iron, or
a ferromagnetic alloy, etc. Second interfitting grooves 66A that
have groove directions in a thickness direction of the second
magnetic guidance members 65A are recessed into upper surfaces of
the second magnetic guidance members 65A so as to have openings.
Here, upper and lower surfaces of the second magnetic guidance
members 65A are mutually parallel flat surfaces. Bottom surfaces
66a in regions of first end portions of the second interfitting
grooves 66A are formed so as to have inclined surfaces that have
gradients that descend toward first ends of the second magnetic
guidance members 65A. The second interfitting grooves 66A are
formed so as to have wedge shapes in which groove widths become
gradually narrower toward the openings.
[0178] The second permanent magnets 67 are fitted into the second
interfitting grooves 66A such that their thickness directions are
oriented in the thickness direction of the second magnetic guidance
members 65A, and first end edge portions of the lower surfaces of
the second permanent magnets 67 are aligned with first end edge
portions of bottom surfaces of the second interfitting grooves 66A,
and are held in the second magnetic guidance members 65A by
applying an adhesive if required. Thus, the bottom surfaces 66a of
the second interfitting grooves 66A and the lower surfaces of the
second permanent magnets 67 face each other in close contact or so
as to have minute gaps, and the second magnetic guidance members
65A and the second permanent magnets 67 are connected magnetically.
The directions of magnetization 40 of the second permanent magnets
67 are perpendicular to the lower surfaces of the second permanent
magnets 67.
[0179] The second magnetic guidance members 65A are fitted into the
second holding grooves 71 such that first end portions are oriented
toward the field coil 14. Here, the bottom surfaces 66a of the
second interfitting grooves 66A and the lower surfaces of the
second permanent magnets 67 are flat surfaces that are tangential
to a truncated conical surface that is coaxial with the rotor 13D.
These flat surfaces are inclined surfaces that have gradients that
are inclined in the axial direction relative to the rotating shaft
16 in directions toward the field coil 14 radially inward from a
radially outer position, i.e., gradients that descend toward the
field coil 14. Because the directions of magnetization 40 of the
second permanent magnets 67 are perpendicular to the lower surfaces
of the second permanent magnets 67, extensions of the directions of
magnetization 40 that pass through the centers of the second
permanent magnets 67 are oriented toward the inner circumferential
surfaces near the tip ends of the facing first claw-shaped magnetic
pole portions 20. First end edge portions of the upper surfaces of
the second permanent magnets 67 are aligned with the second bending
lines 73.
[0180] Consequently, in Embodiment 12, effects can also be achieved
in a similar manner to Embodiment 10.
[0181] According to Embodiment 12, because the bottom surfaces 66a
of the second interfitting grooves 66A are formed into inclined
surfaces that have gradients that descend toward the field coil 14,
the directions of magnetization 40 are perpendicular to the lower
surfaces of the second permanent magnets 67, and extensions of the
directions of magnetization 40 are directed toward the inner
circumferential surfaces near the tip ends of the facing first
claw-shaped magnetic pole portions 20. Thus, it is not necessary to
incline the directions of magnetization relative to the lower
surfaces of the second permanent magnets 67, facilitating
magnetizing of the second permanent magnets 67. Gaps between the
second permanent magnets 67 and the first claw-shaped magnetic pole
portions 20 also become narrower, increasing the amount of magnetic
flux from the second permanent magnets 67, thereby increasing
output.
[0182] Here in Embodiment 12, it is also preferable for the second
magnetic guidance members 65A to be fitted into and held in the
second holding grooves 71 so as to be positioned between points of
intersection O between the second holding grooves 71 and second
bending lines 73 and axial outer end surfaces of the first and
second yoke portions 19 and 23. Because first end portions of the
second permanent magnets 67 enter an inside diameter portion of the
first claw-shaped magnetic pole portions 20 beyond the second
bending lines 73 if the second magnetic guidance members 65A are
fitted into the second holding grooves 71 such that first ends
thereof are aligned with the points of intersection O, the leak
rate of the magnetic flux that originates from the second permanent
magnets 67 can be reduced greatly.
[0183] The bottom surfaces 66a in regions at the first end portions
of the second interfitting grooves 66A are made into inclined
surfaces, but bottom surfaces of the whole interfitting groove may
also be made into inclined surfaces.
Embodiment 13
[0184] FIG. 31 is an end elevation that shows a rotor that can be
used in an automotive alternator according to Embodiment 13 of the
present invention.
[0185] In FIG. 13, first magnetic guidance members 30 are
respectively disposed so as to span eight first trough portions 25.
First permanent magnets 32 are fitted together with and held by
only first interfitting grooves 31 in circumferentially alternate
first magnetic guidance members 30. Here, although not shown,
second magnetic guidance members 35 are also respectively disposed
so as to span eight second trough portions 26 in a second pole core
body 21, and second permanent magnets 37 are fitted together with
and held by only second interfitting grooves 36 in
circumferentially alternate second magnetic guidance members
35.
[0186] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0187] In Embodiment 13, first magnetic guidance members 30 are
disposed so as to span each of the first trough portions 25, and
first permanent magnets 32 are held in circumferentially alternate
first magnetic guidance members 30. Similarly, second magnetic
guidance members 35 are disposed so as to span each of the second
trough portions 26, and second permanent magnets 37 are held in
circumferentially alternate second magnetic guidance members 35.
Consequently, superior reliability can be ensured without
generating gravimetric imbalances relative to centrifugal forces,
and although output is reduced slightly compared to when permanent
magnets are disposed in all of the trough portions, the number of
parts can be reduced, and output can be increased using an
inexpensive configuration.
Embodiment 14
[0188] FIG. 32 is an end elevation that shows a rotor that can be
used in an automotive alternator according to Embodiment 14 of the
present invention.
[0189] In FIG. 14, first magnetic guidance members 30 are disposed
so as to span circumferentially alternate first trough portions 25.
First permanent magnets 32 are fitted together with and held by
first interfitting grooves 31 in each of the first magnetic
guidance members 30. Here, although not shown, second magnetic
guidance members 35 are respectively disposed so as to span
circumferentially alternate second trough portions 26 in a second
pole core body 21, and second permanent magnets 37 are fitted
together with and held by second interfitting grooves 36 in each of
the second magnetic guidance members 35.
[0190] Moreover, the rest of the configuration is configured in a
similar manner to Embodiment 1 above.
[0191] In Embodiment 14, first magnetic guidance members 30 are
disposed so as to span circumferentially alternate first trough
portions 25, and first permanent magnets 32 are held in each of the
first magnetic guidance members 30. Similarly, second magnetic
guidance members 35 are disposed so as to span circumferentially
alternate second trough portions 26, and second permanent magnets
37 are held in each of the second magnetic guidance members 35.
Consequently, superior reliability can be ensured without
generating gravimetric imbalances relative to centrifugal forces,
and although output is reduced slightly compared to when permanent
magnets are disposed in all of the trough portions, the number of
parts can be reduced, and output can be increased using an
inexpensive configuration.
[0192] Now, in Embodiments 13 and 14 above, permanent magnets are
held in magnet holding tools that are disposed so as to span
circumferentially alternate trough portions of each of the pole
core bodies, but permanent magnets may also be held in all of the
magnet holding tools_that are disposed so as to span each of the
trough portions in a first pole core body, and no permanent magnets
held in the magnet holding tools_that are disposed so as to span
each of the trough portions in a second pole core body. In that
case, although output is also reduced slightly compared to when
permanent magnets are disposed in each of the magnet holding
tools_that are disposed so as to span all of the trough portions,
the number of parts can be reduced, enabling output to be increased
using an inexpensive configuration. Because the permanent magnets
are disposed in a well-balanced manner circumferentially,
gravimetric imbalances do not arise relative to centrifugal
forces.
[0193] In Embodiments 1 through 12 above, sixteen permanent magnets
have been explained as being disposed, and in Embodiments 13 and 14
above, eight permanent magnets have been explained as being
disposed, but the number of permanent magnets disposed need only be
set appropriately to match required output. In that case, it is
preferable to dispose the permanent magnets in a well-balanced
manner circumferentially so as not to generate gravimetric
imbalances with respect to centrifugal forces.
[0194] Moreover, in each of the above embodiments, explanations are
given for automotive alternators, but the present invention is not
limited to automotive alternators, and similar effects are also
exhibited if the present invention is applied to dynamoelectric
machines such as automotive electric motors, automotive
generator-motors, etc.
[0195] In each of the above embodiments, the first and second
magnetic guidance members and the first and second permanent
magnets are formed so as to have trapezoidal cross-sectional shapes
perpendicular to the central axis of the shaft, but the
cross-sectional shapes are not limited to trapezoidal shapes, and
for example may also be quadrilaterals of square or rectangular
shape. Moreover, it goes without saying that chamfering or rounding
may also be applied to corner portions of the quadrilateral cross
sections.
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